A lot of materials for an electro-luminescence device have been developed continuously since Tang first developed an electro-luminescence device by a vacuum deposition method in 1987. However, the luminance and thermal stability of the commercialized electro-luminescence device becomes lower when used for a long time, and thus, it is necessary to be improved.
Korean Patent Publication No. 2002-62940 discloses some materials for an organic light emitting diode of an aryl amine compound represented by the following general formula:

U.S. Pat. No. 6,699,599 discloses a light emitting material, in which some or all of hydrogen atoms of Ir(ppy)3 are substituted with deuterium.
In general, when hydrogen is substituted with deuterium, an exciton is more easily generated, resulting in improved luminance efficiency. The reason is as follows. Since the bond strength between carbon and deuterium is stronger than that between carbon and hydrogen, the bond length between carbon and deuterium is shorter than that between carbon and hydrogen when hydrogen is substituted with deuterium. As the result, the Van der Waals force becomes smaller, by which the higher luminance efficiency can be obtained. However, U.S. Pat. No. 6,699,599 as mentioned above does not describe the extent to which the luminescent efficiency has been improved when hydrogen atoms of Ir(ppy)3 are substituted with deuterium atoms.